Allylic derivatives intramolecular carbopalladation

Starting from dimedone, 3-allyl-substituted cyclohexa-l,4-diene-2,4-diyl bisnonafluo-robutanesulfonates have been prepared in four efficient steps. These 1,5-hexadienes under palladium catalysis first undergo intramolecular carbopalladation followed by dehydropalladation to yield a 8-methylenebicyclo[4.2.0]octa-l,4-dien derivative, which subsequently couples intermolecularly with added tert-butyl acrylate. In the presence of... 

As outlined in Sect. B and C, catalytic intermolecular carbopalladations of allenes followed by either /3-hydride elimination or intermolecular nucleophilic trapping provide 1,3-dienes or allyl derivatives bearing the nucleophile moiety, respectively, while an intermolecular carbopalladation followed by intramolecular trapping sequential reaction provides cyclic skeletons (Scheme 27). In Type I, the nucleophilic moiety is connected with the C—X bond, and in lype II it is attached to the allene moiety. 

A one-pot synthesis of 3,3-disubstituted indolines was achieved by taking advantage of a sequential carbopalladation of allene, nucleophile attack, intramolecular insertion of an olefm and termination with NaBPh4 (Scheme 16.6) [10]. First, a Pd(0) species reacts with iodothiophene selectively to afford ArPdl, probably because the oxidative addition step is facilitated by coordination with the adjacent sulfur atom. Second, the ArPdl adds to allene, giving a Jt-allylpalladium complex, which is captured by a 2-iodoaniline derivative to afford an isolable allylic compound. Under more severe conditions, the oxidative addition of iodide to Pd(0) followed by the insertion of an internal olefm takes place to give an alkylpalladium complex, which is transmetallated with NaBPh4 to release the product. 

A variety of 3-vinyl-substituted imidazo[l,5-a]indole derivatives were synthesized by intramolecular Pd catalyzed cyclization of the indole-2-carboxylic acid al-lenamides through either a domino carbopalladation/exo-cyclization process or a novel hydroamination reaction that proceeds smoothly under microwave irradiation. Both the observed pathways involve a Tu-allyl-palladium (II) complex arising from insertion of the allene group into a palladium (II) species, the latter being formed in situ by the intervention of an aryl iodide or of the N-H group. In both these cases, the role of nucleophile is covered by the indole nitrogen (Beccalli et al., 2010). 

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